1. Field of the Invention
The present invention relates to a battery pack and a manufacturing method in which a connector is welded to linearly couple a plurality of batteries.
2. Description of the Related Art
A battery pack with secondary batteries being linearly coupled to one another is used mainly for an electric motor vehicle such as a hybrid vehicle. In the battery pack thus structured, it is important to securely couple the secondary batteries in a manner of a low electric resistance without causing a harmful effect to the batteries. There has been developed a configuration in which a connector made of a metallic plate is welded to linearly couple secondary batteries to make up a battery pack. Refer to Japanese Laid-Open Patent Publication Nos. H10-106533 (1998) and 2001-345088.
A battery pack and its connector 90 disclosed in Japanese Laid-Open Patent Publication H10-106533 (1998) are shown in FIGS. 1 and 2. The connector 90, as shown in FIG. 2, is so structured as to have a metallic plate press-formed into a shape where a tubular side wall 94 is extended along an outer circumference of a bottom face 93. In the connector 90 as shown in FIGS. 3 and 4, the bottom face 93 is spot-welded to a sealing plate 12 on a first battery 10A, and then the tubular side wall 94 is pressed by a welding electrode 40 against a battery casing 11 of a second battery 10B, so that the tubular side wall 94 is spot-welded for coupling to the outer surface of the battery casing 11.
A connector disclosed in Japanese Laid-Open Patent Publication 2001-345088 has several welding projections 81 protruded from both faces of the connector, as shown in FIG. 5. As shown in FIG. 6, for battery connection, the welding projections 81 from both the faces are spot-welded to opposing battery ends of linearly placed batteries 10. A connector 80 used here is attached between the two adjoining batteries 10, and then welded to the end surfaces of the upper and lower batteries by allowing a welding current to flow via the first battery 10A and the second battery 10B, as shown in FIG. 7.